Laser line printer

ABSTRACT

A general purpose printer, particularly suitable for use as an output device for a computer, wherein the paper moves continuously, is disclosed. A belt having an inclined top run carries a mirror in front of the paper. The data to be printed is carried on and is made to operate an array of small laser beams directed at the mirror. By synchronization of paper motion, belt motion, and laser beam operation, straight lines of the data are generated on the moving paper by the continuously moving mirror carrying belt.

, United States Paten 1191 Kaufman et al.

[ 1March 20, 1973 [541 LASER LINE PRINTER [75] lnvent0rs1Craig R.Kaufman; Daniel R.

Strick, both of Pittsburgh, Pa.

Assignee: Craig R. Kaufman, Lois J. Kaufman, Irving R. Kaufman, BenjaminM. Wedner, Daniel R. Strick, all of Pittsburgh, Pa., part interest toBEAM MAN/PULAT/ON 3,523,160 8/1970 Willey ..178/7.6 3,573,847 4/1971Sacerdoti ..346/76 L OTHER PUBLICATIONS Leary, T.G.; Nonimpact RadiantEnergy Priner; IBM Technical Disclosure Bulletin; Vol. 13, No. 9 FebPrimary Examiner-Joseph W. Hartary Attorney-William Kovensky [5 7ABSTRACT A general purpose printer, particularly suitable for use as anoutput device for a computer, wherein the paper moves continuously, isdisclosed. A belt having an inclined top run carries a mirror in frontof the paper. The data to be printed is carried on and is made tooperate an array of small laser beams directed at the mirror. Bysynchronization of paper motion, belt motion, and laser beam operation,straight lines of the data are generated on the moving paper by thecontinuously moving mirror carrying belt.

5 Claims, 6 Drawing Figures 70 PAPER SY/VC DRIVE r MOTOR COMPUTERSPLITTER I LASER LINE PRINTER This invention pertains to a printer, andparticularly such a device suitable for use as high speed output meansfor modern high speed general purpose digital computers. The inventionis not so limited however, and can be used in any application where highspeed printing is needed to follow rapidly changing data, such asfacsimile reproduction, or in data telemetry in general.

The state of the high speed printer art at present is generally a highlyimproved mechanical device involving the creation of characters usinginked ribbon and male dies, i.e., operation essentially that of atypewriter. The improvements involve mounting the type on chains, fasterlinkages, high speed motors, and the like. However, all such essentiallymechanical printing devices suffer from many disadvantages. It is notpossible to easily change the character set or type font insuch,devices. As the number of characters within a character set increases,the time needed to gain access to any given character increases. Stillanother disadvantage of such mechanical printers is the need to causeabrupt changes in direction of motion and rapid increases and decreasesin acceleration in the various parts such as hammers, rachets, rollers,linkages, and the like. Still another disadvantage is the need to imparta line-by-line essentially jerky motion to the paper. Of course, thepaper must come to a complete stop before printing a character,otherwise the imprint will be blurred, and/or the line will not bestraight. This particular kind of deterioration of product quality inhigh speed computer driven printers is quite common. Still anotherdisadvantage of essentially mechanical printers is the deterioration ofthe ribbon with use, and/or the time, expense and annoyance to replacedisposable ribbons.

The newest printers use other means such as electrostatic printing, orspraying ink through dies, but such devices still have many parts whichmove intermittently, and they also move the paper line-by-line.

The present invention provides a printer which overcomes all of theabove disadvantages, and which in addition operates at even greaterspeeds than the fastest printers presently available. Further, it isthought that printers embodying the invention will be very much quieterin operation than such conventional printers. The printer embodying theinvention achieves these improvements, most basically, by providingcontinuous motion of all of its moving operative parts, therebyeliminating all the inherent disadvantages of mechanical directionchanging types of mechanisms. Combined with the continuously movingparts, the invention comprises a light or light-like energy source,preferably a laser, cooperable with light energy responsive paper. Thisportion of the invention, data input, has no moving parts and operatesat electronic speeds. Thus, all of the inherent problems in all die orink based systems are overcome.

The combination of the invention also includes means to utilize theversatility of modern mini-computers, or the versatility of the computerdriving the invention printer, to operate the laser light source in sucha way as to achieve a virtually infinitely variable character set ortype font. The provision of computer or computer-like control of thelaser further permits the printing of halftones so as to permitextensive creation of graphics on an otherwise ordinary output printer.Further, when coupled with the appropriate paper, multi-layered perhaps,the invention could produce full color output.

The printer embodying the invention comprises one or more belt mountedmirrors which are continuously moved in front of the light responsivepaper. The active top run of the belt is inclined with respect to thedirection of paper travel, in a plane parallel to the plane of thepaper, and the belt and paper drives are synchronized together so thatboth move continuously while generating straight lines of data or print.The mirror has a height substantially equal to the height of onecharacter. The laser energy is directedto the mirror and then onto thepaper or other laser responsive medium. The beam from the source isbroken up into a plurality of separate, individually controllablesmaller beams between the laser source and the mirror. By allowingcertain combinations of the smaller beams from the mirror to strike thepaper, with due regard to the timing of the motions of both the belt andthe paper, an infinitely variable character set can be obtained. Becausethe laser beam does not spread or dissipate, and because the charactersare built up from parts rather than imaged, no undue optical or focusingproblems are encountered.

Thus, it can be seen that the printer of the invention is inherentlysmooth in operation because of the continuous motion of both the paperand of the belt driven mirrors. The input of data is done entirelyelectronically in the means which control the small laser beams.

The simplest embodiment of the invention would include two parallel runsof one endless belt, and two mirrors on the belt mounted apart, orequally spaced apart. Since a small fraction of time will exist whilethe first mirror is moving off of the top run of the belt as the secondmirror moves onto the top run of the belt, the printer of the inventionautomatically creates a small vertical space between the lines of dataon the continuously moving paper. The size of this space can be modifiedor even eliminated by making suitable changes in the synchronism betweenthe belt and paper drives, by using additional runs of belt each with anadditional mirror, and/or by reducing the size of the pulleys in thebelt drive system.

The above and other advantages of the invention will be pointed out orwill become evident in the following detailed description and claims,and in the accompanying drawing also forming a part of the disclosure,in which:

FIG. 1 is an overall partially schematic and partially mechanicalshowing of a printer embodying the invention;

FIG. 2 is a schematic expanded view of part of FIG. 1;

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 1;

FIG. 4 is an exaggerated diagrammatic illustration of the word TI-IE asit might be produced by a printer embodying the invention; and

FIGS. 5 and 6 are two other embodiments of the belt drive.

Referring now in detail to the drawing, reference numeral 10 generallyindicates a printer embodying the invention, with some of the partsshown schematically Printer comprises a laser 12, the energy from whichis used in generating the hard copy of the data on paper 14. The use ofa laser as the energy source 12 is preferred because the laser beamconsists of monochromatic and coherent light, thus facilitating dividingthe beam and optically handling it. However, in other applications, theinvention could be made to operate with ordinary light or other forms ofenergy. Whatever energy source is used at 12, it is necessary that thepaper 14 be responsive thereto to produce a hard copy. For example,various kinds of photographic or photographic-like papers could be usedwith laser or ordinary light.

Therefore, the term paper as used in the specification and claims shallbe understood to mean anytrue paper or any paper-like material which iscompatible with whatever particular energy source is being utilized inany particular embodiment of the invention. Similarly, the term laser orlaser energy or light or energy or beam or the like shall be understoodto mean any such light or light-like energy which, with a suitablepaper, can produce hard copies of data. Therefore, the term printing andits derivatives as used'herein shall be understood to mean any set of acompatible paper" and energy beam".

Mounted front of or in otherwise operatively cooperable relation to thefront or sensitive face of paper 14, is a belt assembly 16. In the formshown in FIG. 1, belt assembly 16 comprises a low end pulley 18, a highend pulley 20, a top belt run 22 carrying a mirror 24, and a bottom beltrun 26 carrying a mirror 28. The endless belt assembly 22, 26 ispreferably made of a material which will'permit the mounting of mirrors24 and 28 thereon, which will allow a positive drive, and which will beresistive to changes in length caused by temperature or otheratmospheric changes, while at the same time being highly efficient anddurable in use. A suitable material might be rubber impregnated cottonor high strength metal chain. Such belts'are known in the art to becapable of speeds of several thousands of feet per minute. The means todrive the belt, not shown, may be connected to either pulley 18 or 20,and will be some appropriate conventional belt driving means. is thebelt will run continuously in operation, and must merely be stable andreliable and synchronized with the paper drive, a great deal ofexistingtechnology is applicable to making this part of the apparatus of theinvention, and thus it need not be explained further here, Similarly,the mirrors 24 and 28, see FIGS. 1 and 3, will be mounted at 45 offperpendicular to the paper 14, so as to direct the laser energy onto thepaper while, at the same time able to make the turns around the pulleys18 and 20. Again, such structure iw well within existing technology,and, for example, could be achieved by a rivet or other point-typemounting between mirror and belt.

lnterposed between laser 12 and belt assembly 16 are means 30 forcontrolling the energy from energy source 12 in its travel to themirrors on the belt assembly. Various kinds of structure to manipulatethe beam and to effectually code or input the data onto the beam totransmit the data to the paper 14 are possible, and the preferredembodiment will be described below with regard to FIG. 2. As an exampleof other types of structure in block 30, a fiber optics system includingsome sort of blocking or switching means could be used to code data ontothe beam. The arrow 29 indicates the energy passing from laser 12 to thebeam manipulator 30, and arrow 31 indicates that energy modified byhaving the data to be printed impressed or coded thereon in accordancewith the invention. Thus, the beam 29 from whatever source may bethought of as an energy beam data carrier, with the data ladened orcoded thereon in block 30, and the resultant data carrying energy beamemerging as at 31 parallel to the direction of mirror travel.

A block 32 indicates the overall control for the entire system, whichalso includes a motor 34 and the synchronous drive means 36 for both thebelt and the paper. A computer 38 is shown partially because it does notper se form a part of the invention, since the computer merely drivesthe invention printer. A line 40 interconnects the control circuitry 32with computer 38. A line 42 connects the circuitry 32 to motor 34 andanother line 44 interconnects said control circuitry with thesynchronous drive means 36. A line 46 interconnects the controlcircuitry with the beam manipulating means 30. The interconnectionsbetween the synchronous drive 36 and the belt drive means and the paperdrive means, both not shown, are indicated by the lines 48 and 50,respectively. The two drives, for belt and for paper, may be readilyfabricated using present conventional technology in that both the paperand the belt move continuously. Thus, the lines 48 and 50 may representelectrical power delivered to synchronous or the like motors, or mayrepresent some sort or physical interconnection, such as positivedrives, chains, or the like. The lines 40, 42, 44 and 46, as is wellknown to those skilled in the electronics and electrical arts, mayrepresent an actual wire, a printed circuit board interconnection, orthe like conductor, and may also represent a single or a plurality ofelectrical conductors.

The control circuitry 32 could interact with the computer 38 driving theinvention in various different manners. Where the output to be printedor displayed on paper 14 consists solely of standard alphanumeric data,then it would probably be most efficient to provide the requiredrelatively simple logic or coding needed to transform letters into beamcombinations within the control circuits 32 themselves. It iscontemplated that using modern solid state electronics, the necessarylogic would require no more than one or two printed circuit boards orperhaps a small number of integrated circuits; This first mode orembodiment of circuitry 32 has the advantage of being very easilycompatible with many different kinds of computers or other input devicesbecause the input data on the line 40 is simply a signal representativeof the actual letter or number to be displayed in some conventionalcode. The corresponding disadvantage of this first form of circuitry 32is that it is fairly limited in scope. A second form which circuitry 32might take would be simply switching circuits for the computer 38. Inthis case all of the coding, timing information, and the like, wouldhave to be programmed into the computer represented at 38. This form hasthe advantage that a virtually infinite variety of final output ispossible, including virtually any kind of graphical display, but has thedisadvantage that having only switching circuits in block 32 makes theprinter less universally compatible. Still a third form which thecircuitry 32 might take, and perhaps the most desirable, would be somecombination of the first two forms. For example, block 32 could includethe logic for several fonts of characters, and some limited graphics,but also means to convert to purely a switching function if moresophisticated displays under the direct control of the driving computerare desired.

If desired, a tape buffer could be provided between computer 38 andblock 30. The read head would be synchronized with the printer and thewrite head with the computer, whereby the speeds of computer and printerwould be substantially independent of each other.

Referring now to FIG. 2, there is shown the preferred form of the beammanipulation means or data coding means 30. The raw laser energy 29first encounters a beam splitter 52 which divides the single beam fromlaser 12 into a plurality of smaller beams, as indicated on the drawing.Beam splitter 52 may take the form of a fiber optical device, an arrayof optical wedges, an array of mirrors, or the like, as is well known tothose skilled in the art.

Means are provided to individually control the separate small beamsproduced after the beam splitter and to impress the input data on saidseparate beams. To this end, there is provided a first array of prismsS4 and a second array of prisms 56. The prisms serve to align the smallbeams so they may be more readily handled by the electronic lightmodulators 58. The line 46 fromthe control circuitry 32 operates themodulators 58. The modulators may be thought of as high speed electroniclight shutters which individually control the small beams after the beamsplitter. One device which -is thought to be usable as the modulators 58is produced. by Isomet Corporation of Palisades Park, N.J., their MOdelNo. EOLM-400. This device has a rise time of l nanosecond. The smallbeams, with the input data impressed thereon by selective operation ofvarious combinations of the modulators 58, are brought together again,after the second prisms 56, by a collimator 60, the output of which isthe data carrying beam 31. Thus, it can be seen that the function of thebeam splitter 52 and the two sets of prisms 54 and 56 is to generatesufficient physical separation between the small beams so that they maybe individually handled by the modulators 58. If other technology wereavailable, the beam splitter, the various prisms, and perhaps even thecollimator, could be combined, as is obvious.

An important feature of the invention is achieving continuous operationof both the belt 22 and the paper 14 is the difference in heightindicated by dimension R on FIG. 1 between the centerlines of thepulleys 18 and 20. The same dimension R appears in FIGS. 5 and 6described below. The drawing is not to scale, but dimension R would besubstantially equal to: (1) the height of a single mirror 24 or 28, (2)the maximum height of a single character, and (3) the height of thearray of small beams 31 as generated by the beam manipulation means 30.The drawing was intentionally made so as to more clearly show how thebeams 29 and 31 from the laser are parallel to the top run of the belt22 without regard to scale.

Referring to FIG. 4, there is shown, somewhat schematically, the wordTI-IE as it might beproduced by aprinter embodying the invention. Thecontrol circuitry continuously senses the position of the continuouslymoving mirror 24 by means of the positive belt drive. When the mirror isin the position wherein the beams 31 reflected therefrom onto the paperwould produce dots at the vertical location corresponding to mark 62 inFIG. 4, then at precisely that time the control circuitry will close offall but the uppermost modulator 58 and its small beam. Operationcontinues in this manner until the mirror arrives at the positioncorresponding to the marks 64, at which time all the modulators open topass their respective small beams to thereby produce the vertical leg ofthe letter T. As can now be appreciated, the rise in the belt R allowsthe data ladened beam 31 to effectually follow the motion of paper 14 toproduce a straight line of data, the necessary timing being produced bythe synchronous drive 36 under the guidance of the control circuitry 32.While this timing is highly critical, it is relatively easily obtainedbecause belt and paper are driven both continuously and positively.Along this same line of thought, speed control would be readilyachieved. A

. warm-up period will probably be needed to allow belt and paper toarrive at an operating speed at start-up.

If the modulators 58 are driven so as to be operated in a proportionalrather than an on/off mode, then it can be readily appreciated how theprinter of the invention can produce halftone graphics, and othersophisticated displays. Further, examining FIG. 4 again, since the dotsare quite small, and a large number of them are needed to make up anyletter, it is readily appreciated that these relatively small buildingblocks can be put together 'to form scientific symbols, Chinesecharacters, or whatever else might be desired.

For purposes of example, the drawing illustrates breaking the beam 29into eight small beams, to thus produce a vertical array 31 eight smallbeams high, which, it is thought, would be sufficient for most purposes.If simpler material is to be printed then perhaps an array only fivesmall beams high would be satisfactory. Conversely, if still moresophistication is required then a number greater than eight beams couldbe provided, with a concomitant increasein cost and complication. In anycase, the individual spots or marks such as 62 and 64 will be formed andspaced so as to produce actual or apparent solid lines on the paper 14.The small beams could have a rectilinear cross-section for this purpose.FIG. 4 shows separate discrete marks for purposes of illustration only.

As can be readily appreciated from the drawing and the aboveexplanation, no printing can occur during the time a mirror goes OR thetop run around the pulley 20 and until the time another mirror comesinto the top run around the pulley. 18.Since the paper is movingcontinuously, this dead time automatically produces a space on the paper14 extending perpendicular to the direction of motion of the paper. IFsuch a space is desirable in a particular useage, then it can beenlarged by simply using a two run belt system as in FIGS. 1 and 3, andproviding relatively large diameter pulleys 18 and 20. In otherapplications it may be desired to minimize the size of this space tothereby more efficiently pack data onto the paper 14. Referring to FIGS.

and 6, there is shown two alternative means to accomplish the latterdesideratum.

The belt 22a of FIG. 5 is of triangular configuration and has the samerise R in its top run. By providing a belt with additional runs eachcarrying an additional mirror, the dead time when a mirror is not on thetop run is made smaller. In FIG. 6, there is shown a belt 22b having 4runs, 4 mirrors, and again the same rise R. Another way to minimizenon-printing time, irregardless of the number of runsin the belt, is tosimply decrease the diameter of the upper left pulley, i.e., the top runpulley closest to the energy source. The rise R is related to characterheight and not the number of belt runs.

While the invention has been described in detail above, it is to beunderstood that this detailed description is by way of example only, andthe protection granted is to be limited only within the spirit of theinvention and the scope of the following claims.

We claim:

1. Apparatus for printing data on paper comprising means forcontinuously moving the paper in a first direction and in a first plane,means for continuously moving mirror means in a second plane parallel toand displaced from said first plane and in a second direction, saidsecond direction being substantially perpendicular to said firstdirection and having a relatively small component parallel to said firstdirection, means for coding the data to be printed into an energy beamcarrier, means for directing said data ladened energy of said energybeam carrier in said second direction to said mirror means and thenceonto said continuously moving paper, said data coding means comprisingmeans for dividing said energy carrier into a plurality of smallerenergy beams, means for individually controlling the state of each ofsaid smaller energy beams in accordance with said data and a code, andmeans for arranging said controlled smaller energy beams into a lineextending in said first direction.

2. The combination of claim 1, said mirror means moving means comprisingan endless belt having a predetermined number of runs and an equalnumber of mirrors equidistantly spaced on said belt, one run of saidbelt extending in said second direction, positive drive means forpositively driving said belt, and synchronization means forsynchronizing said belt drive means and said paper moving means.

3. The combination of claim 1, said component of said second directionparallel to said first direction being of such a size with respect tothe paper dimension perpendicular to said first direction thatthe riseof said mirror means in its motion across said paper is substantiallyequal to the dimension of said mirror means in said first direction andsubstantially equal to the maximum height of a single data character asprinted.

4. The combination of claim 1, wherein said energy beam carriercomprises eight of said smaller energy beams.

5. The combination of claim 1, wherein said energy beam carriercomprises alaser, and an electronic light modulator for controlling eachof said smaller laser beams.

1. Apparatus for printing data on paper comprising means forcontinuously moving the paper in a first direction and in a first plane,means for continuously moving mirror means in a second plane parallel toand displaced from said first plane and in a second direction, saidsecond direction being substantially perpendicular to said firstdirection and having a relatively small component parallel to said firstdirection, means for coding the data to be printed into an energy beamcarrier, means for directing said data ladened energy of said energybeam carrier in said second direction to said mirror means and thenceonto said continuously moving paper, said data coding means comprisingmeans for dividing said energy carrier into a plurality of smallerenergy beams, means for individually controlling the state of each ofsaid smaller energy beams in accordance with said data and a code, andmeans for arranging said controlled smaller energy beams into a lineextending in said first direction.
 2. The combination of claim 1, saidmirror means moving means comprising an endless belt having apredetermined number of runs and an equal number of mirrorsequidistantly spaced on said belt, one run of said belt extending insaid second direction, positive drive means for positively driving saidbelt, and synchronization means for synchronizing saId belt drive meansand said paper moving means.
 3. The combination of claim 1, saidcomponent of said second direction parallel to said first directionbeing of such a size with respect to the paper dimension perpendicularto said first direction that the rise of said mirror means in its motionacross said paper is substantially equal to the dimension of said mirrormeans in said first direction and substantially equal to the maximumheight of a single data character as printed.
 4. The combination ofclaim 1, wherein said energy beam carrier comprises eight of saidsmaller energy beams.
 5. The combination of claim 1, wherein said energybeam carrier comprises a laser, and an electronic light modulator forcontrolling each of said smaller laser beams.